Dinan S3-R BMW M3

Dr. Dinan cooks up a spicy M3.

Back in the 1970s, a collegian named Steve Dinan kissed off an engineering career to bust his knuckles pumping up BMWs. One of his turbocharged Ultimate Driving Machines first laid a patch on these pages in 1988, and since then, we’ve tested eight Dinan BMWs, more or less melting for them all.

The S3-R M3 is emblematic of the type of audacious tinkering we expect from Dinan Engineering’s workshop in Morgan Hill, California—and the kind of prices. Order everything from Dinan, including the engine, suspension, brakes, wheels, fries and a Coke, and the bill comes to $47,836. That is, after you’ve purchased a $60,575 BMW M3 coupe and $1806 in new tires.

Yes, it’s just a wee bit spendy, but this is no casual slap-on of carbon-fiber flounces and plastic galloons. (Dinan offers at least four variations on this theme, from the highly souped-up S3-R to the cosmetic-only S.) The M3’s stock 4.0-liter V-8—a Valjoux 25-jewel chronograph among car engines—is yanked right out, its major organs eviscerated. This, ahem, voids BMW’s warranty, but Dinan takes over and ensures its work for the same four years or 50,000 miles. Dinan, which also builds BMW’s Daytona Prototype racing engines, then repacks the block with a billet crank, forged pistons, and lighter connecting rods. In the event, the bore widens by two millimeters, to 94, and the stroke lengthens by 7.8 mm, to 83.

Thus, in the $31,234 engine portion of the S3-R makeover, Dinan adds 609 cc of displacement, rechambering the engine into the car as a 4.6-liter. Dinan also bores out the throttle bodies (for greater airflow) and fits a smaller, lightweight crank pulley to lessen parasitic power loss from the water pump, the A/C compressor, and the alternator.

Finally, for this particular car, Dinan bolts on a larger, low-restriction air intake and replaces the exhaust midsection with the company’s own stainless-steel “racing” exhaust (i.e., no catalytic converters), which spits thunderclaps and lightning.

With all the internal changes and external tchotchkes, the power subsequently mushrooms, especially in the middle. The S3-R M3 peaks at 527 horsepower at 7800 rpm, Dinan claims, up 113 and down 500 rpm from stock. Perhaps more significantly, the stock torque figure of 295 pound-feet rises by 112, to 407, though the torque peak also rises, from 3900 rpm to 5200.

With tuner cars, the question always comes down to numbers. Dinan’s power figures are predicated on 93-octane gas, which is nearly unobtainable in 91-only California, where we gave the S3-R M3 its test-track licking. Even so, it should have enough extra power to chisel time off the stock M3’s ETs.

Well, the results proved complicated.

Dinan figured we’d turn a quarter-mile in the low-12-second range, rather than the 12.5 seconds we in fact posted, at 118 mph. The many stock, manual-transmission M3s we’ve tested have been only slightly slower (12.6 to 12.9 seconds).

Doing the pathology on the numbers, we realized that the S3-R M3 cost itself time at the line, spinning its tires. Power is nothing without traction, and the car seems to ride atop its own permanent ice cap. On dusty desert pavement, it easily breaks loose its fat Michelins in first and second gears, so it’s no easy car to get out of the hole.

We were slower to 30 mph than in most other M3s we’ve tested, but then the S3-R M3’s power showed, reeling in the stockers and passing them by 60 mph. The tuned car hit 60 in 4.2 seconds, about two-tenths quicker than most of the stock M3s we’ve tested. A better test surface would certainly make for a better launch, and the Dinan M3 would be quicker at the key marks, no question.

With catalytic converters? Dinan says that would cut 23 horses, but running on 93 octane would add 15, so it shouldn’t make much of a difference.

If you can’t spring for the engine, there’s always the far less expensive “Stage 3” suspension package ($2964) and Brembo brake pack ($7645). Dinan fits its own shortened springs, a larger front anti-roll bar, new bump stops, replacement front camber plates with greater adjustability, a carbon-fiber strut brace, and billet-aluminum adjustable rear toe-control links with Heim-joint attachments. These are stiffer than the forged stock units and their rubber bushings, which allow rear-end squirming under acceleration.

The S3-R M3 sits a half-inch lower, but Dinan, as always, takes care to retain the factory ride quality by raising the spring purchases a half-inch, thus retaining the stock suspension travel.

The result is an M3 limbered up for track work but still livable on a city’s imperfect surfaces. It plugs into corners with even more exuberance, sloshing your innards against your ribs and putting more crispness into the steering with less body roll. And there’s no trace of plow exiting turns, as the Dinan is more inclined than the stock M3 to lose grip at the rear rather than at the front, thanks partly to the stiffened toe-control links. In terms of immediately noticeable change, the suspension pack is a great value, and, like everything here, you can order it from Dinan a la carte.

Even if we can’t make it go as fast as it should, the S3-R M3 still offers Porsche perform­ance, albeit at Porsche prices. For those who prefer their speed served Bavarian style, Dinan has something to lust after.

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